The Problem: Seawater intrusion through the Port Stabilizer assembly.

The Problem: Seawater intrusion through the Port Stabilizer assembly.

July 2011

The Problem: Seawater intrusion through the Port Stabilizer assembly.

After departing from Ashiya, Japan on May 5, I noticed that there were a few drops of salty water dripping from the top of our port stabilizer. I first checked the torque of all of the bolts that were accessible, and then put a small bowl below the unit and monitored the flow hourly. This was a slow leak, maybe a tablespoon a day. About 600 nm out of Ashiya we stopped at Chichijima and I dove under the boat and found some large mussels wedged between the top of the fin and around the shaft; I wondered if maybe a piece of mussel shell was wedged into the seal? Naiad assured me that the fit is much too close than what would allow pieces of shell into the space occupied by the seals. The dripping stopped after about a week of running.

The trip to Hawaii took 24 days. Upon our arrival in Honolulu I made arrangements to haul out. The bottom needed paint and after two years and 15,000nm of running, it was time to check the stabilizer seals. Starr was hauled out at Keehi Marine Center.

Starr Haul-out (click to enlarge any picture)

I pulled the fins with tools I carry on board: a 10 ton hydraulic power pack, a 600Ft Lb torque wrench, and all of the necessary tools to do our own work.

Note: see the excellent article on seal replacement by Scott Flanders, Voyage of Egret 7-21-2011

The last time I pulled the stabilizer system and replaced the bearings was in 2001 in New Zealand. At that time I was 58 yrs old and now I am 68. THIS WAS NOT MY IDEA OF FUN!! I have a great deal of respect for the Naiad factory people from Seattle, and I would have liked them to do the job; unfortunately, they were all committed elsewhere. I decided that I would have to do the work myself. SOME PEOPLE NEVER LEARN.

Naiad diagram of our 302 stabilizers (click to enlarge)

Port stabilizer showing leak trail. (click to enlarge)

(click to enlarge)

After popping the fins off, I pulled the seals. My first observation was that the seals were heavily coated with RTV, even into the expansion “V” grooves, and didn’t even come close to resembling the factory recommendations.

I removed the seals using a power screwdriver and 3-inch screws. The seals were packed on all sides with RTV.

Factory Seal install procedure (click to enlarge)

As you can see, the seals were improperly packed full of RTV when they were last replaced in Seattle two years ago. I don’t think it’s a poor guess to think that the expansion/flexing space in each of the seals was “locked up” with the RTV being jammed throughout the whole seal assembly. Even though it was obvious that the seals were improperly installed, it was impossible to clearly determine the condition of the grease. The only way to be sure was to pull the bearing retainer plate to see if the grease was contaminated.

With the bearing retainer plate removed, it was clear to see that the previously white grease was now black with contamination.

The bearing retainer is removed and the white grease has turned black with seawater contamination showing. (click to enlarge)

The next task was to drop the shaft in order to get to the bearings, and see if the seawater had damaged them. To accomplish this I had to work my way down from the top, starting with the potentiometer, then the cover plate, (I was careful to lift the cover plate evenly so as to not break the hydraulic ram trunion roller bearings), then the torque arm, and finally the seal wiper and seal. When the shaft was loosened it didn’t want to drop out so I made a driver out of heavy-walled stainless pipe and drove it out with a 5# sledge hammer. Once the shaft was out, the next job was to pull the sleeve and the bottom bearing. This was made easier by using a puller made from ¾-in all-thread, and a heavy bottom plate and a top plate of a slightly smaller diameter than the sleeve OD. With the sleeve and bearings removed, I examined the bearings and determined that they had damage from the water intrusion. New bearings and races were delivered the next day from Naiad’s factory. Yay Naiad!

Shaft and bottom bearing with seawater contaminated grease. ( click to enlarge)

Top Seal and wiper where seawater was exiting. (click to enlarge)

Sleeve and bottom bearing. (Note that the grease is clean on the sleeve exterior. The water went in between the shaft and the sleeve.)

Port actuator

Port actuator with sleeve out, and bearing races still in place. I took them out using a 1½-inch x 18-inch bronze driver (cut from an old prop shaft).

Working on the starboard actuator. (If only the guys who design and build boats had to repair each piece of equipment, then access would be different!)

New bearings and races: Due to the close tolerances between the bearing and sleeve one must either use a press or heat the bearings.

Freezing the sleeves.

Heat the bearings to 200 degrees F for 2 hours (and then baste twice).

Dinner is served: Hot and cold entrée!

Viola! The only other way to get the bearing on was to press them on. This is much more fun!

Time for reassembly: Tap the top-bearing race into the housing, then grease the sleeve and pack the bearings. (It was not possible to get the Lubriplate grease that Naiad specifies in Honolulu, so I had S3 ship it overnight from Seattle).

It was necessary to make up a puller using (5) 7/16” fine all-thread bolts to suck the sleeve and bottom bearing back into position.

At this point it was time to replace the seal and wiper, and then to preload the sleeve into its bearings. Unlike with many shaft/bearing installations, no shims are needed in this assembly because Naiad is able to control the dimension of the sleeve so precisely during their manufacturing process.

After reinserting the shaft, I chose to raise it up another 3/8 of an inch so that the bottom seals would ride on new shaft surface material.

It is important to keep in mind that the only thing holding the shaft and the stabilizer in the boat are the two torque arm side-bolts which are torqued to 95Ft Lbs. (see bolt #42 and 43 in the Naiad shop drawing above) that squeeze the torque arm around the spines milled into the top of the shaft .

While it may look like the large nut on the top of the stabilizer shaft is doing the job of keeping the shaft in the boat, IT IS NOT!!! Its principal job is to act as the shaft height adjustment nut. The real shaft retaining work is done by the squeeze the torque arm is performing around the shaft splines.

The balance of the reassembly went quite fast, as did the final realignment of the potentiometer so the center lock pin drops in place as it should.

The sleeve and bearing package is preloaded to 60 FT Lbs torque.

Buttoning up.

Almost done. What a beautiful bottom!!

Dave Schmidt and I cleaning the fin shaft and pocket with brake cleaner.

Up a smidge please.

Torque to 300 Ft-Lbs

Do we make the fin parallel with the keel? Why not toe it out a bit? What is the water flow like at the stabilizer? Let’s toe it out about 3 inches!

Twenty gallons of bottom paint later: I decided to use International 640, but will it work? After asking the local commercial fleet operators, it looks like a coin-toss on what bottom paint works best here in Hawaii.

Splash time.

You can be assured that the next time that the seals need to be replaced, the work will be done by someone else but I will be there watching!!

A BIG THANKS to my SENSEI: Even though Dick McGrew, Naiad’s Pacific Ocean Tech was on vacation, he would respond to my many telephone calls with my questions; and Doug Janes ,who has been doing Naiads since Naiad started, was, and is, an invaluable source of knowledge, help, and support!!

Dick McGrew

Technical Services Manager for the Pacific

Naiad Dynamics

206 359 0500

Doug Janes

J3 Systems

425 345 1470

Ryan Parker


206 491 1595
  • Farley Shane
    Posted at 19:44h, 30 September Reply

    Thanks Don for the detailed description of the repair. It was very interesting.
    Blessings, Farley Shane

  • Dan Freedman
    Posted at 22:01h, 30 September Reply

    Well, I don’t think you can get much more of a demonstration of yachting being “fixing boats in exotic places” than that. Very informative indeed.

    I’m hoping you got to enjoy some of the islands’ bounty while you were here.

  • Viktor
    Posted at 23:48h, 30 September Reply

    Don –

    you ruined it for me! Here I was all inspired by you to do my own stabi work, and now I hear you say “don’t try at home”..By the way – is RTV what I think it is – silicone?

    Anyway, thanks for the detailed description & pictures. I’m so glad we didn’t have to mess with it on our trip!


  • dta
    Posted at 22:24h, 03 October Reply

    Great stuff, definitely needed doing or you’d start to get into risky territory. Admirable machining form Naiad.

  • Ken Williams
    Posted at 10:30h, 13 October Reply

    not sure where to post this: RE: fouling sea chest

    check out they provide a solution for a fouling sea chest. jon

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